1. Field of the Invention
This invention relates to a stitch data producing apparatus for producing stitch data for controlling the operation of an embroidery sewing machine.
2. Description of the Related Art
A conventional embroidery sewing machine that automatically embroiders a pattern onto a workpiece is controlled according to stitch data specifying a stitching point for each stitching cycle. A stitch data producing apparatus for producing the stitch data controlling the embroidery sewing machine comprises a main unit including a microcomputer, and an image reading device, generally an image scanner, which is connected to the main unit. The main unit functions as an image processing apparatus.
The stitch data producing apparatus produces stitch data by processing image data obtained by scanning an original picture of an embroidery pattern with the image scanner or the like. Since the image provided by the image scanner is a bitmap image., shape defining data defining the shape of each pattern represented by the image data needs to be extracted from the bitmap image so the shape of the pattern represented by the image data can be recognized and for advanced graphic processing, including transforming, dividing, combining, enlarging and reducing one or more embroidery patterns.
Generally, the shape representing data of a pattern having some area is outline data or border line data, i.e., data representing a curved and/or polygonal shape representing the border line of the pattern. A conventional method of obtaining such shape defining data, i.e., border line data, requires an operator to manually trace the border line of a pattern displayed on the screen of a display with a pointing device, such as a mouse. Another method automatically extracts the border line by processing the bitmap image by a border line tracing process. Then, stitch data is produced based on the border line data to fill the space enclosed by the border line. The produced stitch data can specify, for example, filling the enclosed area with satin stitches.
When the pattern is a character or a symbol defined principally by lines, some methods describe the pattern by data representing the lines defining the pattern, i.e., short-vector data. Such data, i.e., shape defining line data, is obtained by tracing the middle line between the lines defining a pattern displayed on the screen of a display with a mouse or the like, or by subjecting the bitmap image to a linearizing process. Stitch data for forming stitches, such as zigzag stitches or running stitches, suitable for forming a line pattern, is produced on the basis of such shape defining line data.
Generally, in such an image processing apparatus or such a stitch data producing apparatus, all sorts of patterns, including pictures, characters and such, are provided. For example, a pattern of a rainfall symbol, as shown in FIG. 4, includes a partial pattern A1 representing a rain cloud and having an area, and partial patterns A2 to A4, which are line patterns and represent rainfall.
The operator needs to give appropriate instructions according to the shapes of the patterns when extracting the shape representing data by a manual scanning operation to produce stitch data by the aforesaid stitch data producing apparatus (image processing apparatus). Such a manual scanning operation requires skill and, when the patterns have complicated shapes, much time. If border line data or shape defining line data is extracted automatically according to a predetermined algorithm, the troublesome operator's work is unnecessary. However, shape representing data satisfactorily representing the type and the shape of a pattern cannot necessarily be obtained unless a border line tracing process or a linearizing process is properly selected according to the type and the shape of the pattern and, in some cases, appropriate stitch data cannot be produced.
When line patterns, such as the partial patterns A2 to A4 representing threads of rain shown in FIG. 4, are represented by border line data, stitch data that fills up the space enclosed by the border line with satin stitches is produced on the basis of the border line data and, consequently, an embroidered pattern of an inferior quality is formed. On the other hand, when the partial pattern A1 representing a rain cloud is represented by shape defining line data, the shape of the pattern is deformed significantly and data correctly representing the shape of the pattern cannot be extracted. Accordingly, either the process using the shape defining line data or the process using the border line data must be selectively used according to the shape of a pattern.